Occupant sensing apparatus

ABSTRACT

An occupant sensing apparatus for use in an occupant restraint system comprises a film having an electrical characteristic with changeable states and a contact member. When an occupant sits in a vehicle seat, the contact member pushes on the film and changes the state of the electrical characteristic. An electric circuit is connected to the film for providing a first signal when the film indicates an occupant is not present, a second signal when an occupant is present, and a third signal if the film and the circuit become disconnected. The occupant restraint system is enabled when either an occupant is present or an electrical fault condition occurs. In accordance with another embodiment of the invention, an array of sensors located in the seat determines the occupant&#39;s position and weight and controls deployment of the occupant restraint system in response to the determined position and weight.

This is a divisional of application Ser. No. 07/682,908 filed on Apr. 4,1991 now U.S. Pat. No. 5,232,243.

TECHNICAL FIELD

The present invention is directed to a vehicle occupant restraint systemand is particularly directed to an occupant sensing apparatus in anoccupant restraint system.

BACKGROUND OF THE INVENTION

Occupant restraint systems for use in vehicles are well known in theart. One such restraint system includes a crash sensor, an inflatableairbag, and an actuation circuit that controls deployment of the airbagin response to an output from the crash sensor. The crash sensor can bean accelerometer that provides an electrical signal having a valuefunctionally related to the vehicle's deceleration. The actuationcircuit includes a squib operatively connected to a source of inert gas.

During a crash condition of a vehicle, the vehicle's accelerometerprovides a signal indicative of such crash condition. The actuationcircuit thereby applies a current through the squib which causes thesquib to ignite. When the squib ignites, the source of inert gasdischarges gas into the airbag, which results in inflation of theairbag.

Certain vehicles have both a driver side airbag and a passenger sideairbag ("dual airbags"). If such a vehicle is occupied only by thedriver and is involved a crash, deployment of the passenger side airbagis unnecessary. Unnecessary deployment of the passenger side airbag canincrease the cost of repairing the vehicle. Since a large percentage ofvehicles on the highway are occupied by only the driver, it is desirableto (i) be able to detect if a passenger is present in the vehicle and(ii) deploy the passenger side airbag during a crash only if thepassenger is, in fact, present.

The prior art has recognized the problem of unnecessary deployment of apassenger side airbag during a crash when no passenger is present. Priorart occupant restraint systems having dual airbags have provided variousforms of occupant sensors and have enabled the passenger side airbagonly when an occupant is present in the passenger seat.

SUMMARY OF THE INVENTION

The present invention is directed to a new and useful occupant sensingapparatus. An occupant sensing apparatus, accordance with the presentinvention, permits detection of (i) whether a vehicle seat is occupied,(ii) Whether an object in the seat is animate or inanimate, (iii) theweight of an occupant, (iv) the position of an occupant in the seat, and(v) whether there is an electrical fault condition such as an electricopen or short circuit in the occupant sensor. An occupant restraintsystem, having the occupant sensing apparatus of the present invention,is enabled if either an occupant is present or an electrical faultcondition exists in the occupant sensor. The passenger side airbag ispositioned, i.e., aimed, in response to the detected position of theoccupant. The deployment of the airbag is controlled in response to theweight and position of the occupant.

In accordance with one embodiment of the present invention, an occupantsensing apparatus for an occupant restraint system comprises (a) a filmhaving an electric characteristic with changeable states, and (b) acontact member. Means are provided for mounting the film and the contactmember in a vehicle so that presence of an occupant effects physicalcontact between the contact member and the film. The electricalcharacteristic of the film has a first state when there is no contactbetween the film and contact member and a second state when there iscontact between the film and the contact member. Electric circuit meansare connected to the film for providing a first signal when the film hasthe first state indicative of an occupant not being present, a secondsignal when the film has the second state indicative of an occupantbeing present, and a third signal when the film does not have the firstor second state, thereby indicating that an electrical fault conditionexits. The sensor further includes means for enabling the occupantrestraint system when either the second signal or the third signal isprovided by the electric circuit means.

In accordance with a preferred embodiment, the film is a piezoelectricfilm. The electric circuit means provides an unstable feedback looparound the piezoelectric film so that the film provides an electricoutput signal that oscillates. Contact between the contact member andthe film effects a change in the output signal from the film. Theelectric circuit means provides the first, second, and third signals inresponse to the output signal from the film. Contact between the contactmember and the film attenuates the oscillations. The oscillations arepreferably within a predetermined frequency band and the electriccircuit means includes a band pass filter designed to respond to thepredetermined frequency band. The predetermined frequency is 2kilohertz. Preferably, a plurality of such piezoelectric films aremounted in a checker-board pattern with a plurality of individual forcesensing resistor films so as to monitor weight and position of theoccupant.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the present invention will become apparent to thoseskilled in the art to which the present invention relates from readingthe following specification with reference to the accompanying drawings,in which:

FIG. 1 is a schematic of an occupant restraint system made in accordancewith one embodiment of the present invention;

FIG. 2 is top plan view of a film sensor made in accordance with thepresent invention with certain parts removed for clarity;

FIG. 3 is a sectional view along line 3--3 of FIG. 2;

FIG. 4 is an exploded view of the film sensor shown in FIG. 2;

FIG. 5 is a circuit schematic of an occupant restraint system made inaccordance with one embodiment of the present invention;

FIG. 6 is a circuit schematic showing the film drive circuit shown inFIG. 5;

FIG. 7 is a circuit schematic showing the band pass filter circuit shownin FIG. 6;

FIG. 8 is a graphical representation of the output of the drive circuitshown in FIG. 6;

FIG. 9 is a schematic of an occupant restraint system made in accordancewith another embodiment of the present invention;

FIG. 10 is a top plan view of the occupant position and weight sensorshown in FIG. 9;

FIG. 11 is a side sectional view of the occupant position and weightsensor taken along line 11--11 of FIG. 10;

FIG. 12 is a circuit schematic of a portion of the occupant restraintsystem of FIG. 9;

FIG. 13 is a circuit schematic of a portion of the occupant restraintsystem of FIG. 9;

FIG. 14 is a graph of resistance of the weight sensor shown in FIG. 9;

FIG. 15 is a graph of the change of resistance of the weight sensor as afunction of the weight of the occupant;

FIG. 16 is a graph of the percentage of gas discharged from the airbagshown in FIG. 9 as a function of distance between the occupant and thedashboard or as a function of the weight of the occupant;

FIG. 17 is a graph depicting the angular position of the airbag shown inFIG. 9 as a function the occupant leftward and rightward position in thevehicle seat;

FIG. 18 is a graph depicting the angular position of the airbag shown inFIG. 9 as a functions the occupant forward or rearward position in thevehicle seat;

FIG. 19 is a graphical representation of the output of the humanisticsensor shown in FIG. 9;

FIGS. 20-22 are flow charts depicting the control process followed bythe controller shown in FIG. 9; and

FIG. 23 is a top plan view of a position and weight sensor in accordancewith another embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring to FIG. 1, an occupant restraint system 20 includes an airbagassembly 22 mounted in an opening of a dashboard 24 of a vehicle. Theairbag assembly 22 includes a airbag 26 folded within the interior of anairbag housing 28. A cover 30 covers the airbag and is adapted to openeasily upon inflation of the airbag 26.

A source 32 of inert gas is mounted at the back of the housing 28 and isoperatively connected to the airbag 26. Gas discharged from the source32, which may be generated by combustion of pyrotechnic material orsimply released from a pressurized container, fills the airbag 26 to itsinflated condition 26'. Once inflated, as occurs during a vehicle crash,the airbag 26 cushions an occupant located in a vehicle seat 34.

An electronic controller 36, such as a microcomputer, is operativelyconnected to a vehicle crash sensor 38. The crash sensor 38 can be anyof several known types. For example, the crash sensor 38 may be amechanical inertia switch, such as a rolamite sensor, or an electricalaccelerometer. If a normally open inertia switch closes, this is anindication that a crash is occurring. Likewise, if a signal from anelectrical accelerometer reaches a predetermined level or apredetermined level for a predetermined time, this is an indication thata crash is occurring. Once the controller 36 determines that a vehiclecrash is occurring for which deployment of the airbag is necessary toprotect the vehicle occupants, the controller 36 ignites squib 40 which,in turn, actuates the gas source 32.

The occupant seat 34 with which the occupant restraint system 20 is usedis preferably the passenger seat in the vehicle. The seat 34 includes anoccupant sensor 60 located in the bottom cushion 42 of the seat 34. Theoccupant sensor 60 is used to control whether deployment of the airbagis to be prevented.

FIGS. 2-4 show one embodiment of the present invention, including anoccupant presence sensor 60. The sensor 60 includes a housing 90 whichincorporates a bottom support plate 92 and a top cover plate 94. Thebottom plate 92 is rigidly mounted to a substantially inflexible bottomportion of the seat 42.

The bottom plate 92 and the top plate 94 include interior surfaces 96,98, respectively, which are spaced apart. An annular sealing member orgasket 100 is mounted between the support plate 92 and the upper plate94. The sealing member 100 includes a central opening 106. The plates92, 94 are secured together by means of a plurality of spaced apartscrews 102. Specifically, the top plate 94 has holes 103 and the bottomplate 92 has threaded holes 104. The gasket 100 has corresponding holes105. The screws 102 extend through the holes 103 and 105 and are screwedinto the holes 104. The bottom plate 92, the upper plate 94, and thesealing member 100 form a chamber 107 in which a piezoelectric filmsensor 110 is mounted.

The bottom plate 92 includes a recessed portion 112. The piezoelectricfilm sensor 110 spans the recess 112 and is secured along opposed edgesat locations 114, 116 by appropriate means, such as adhesive. The bottomplate 92 further includes a second recessed portion 120. A film drivecircuit 122 is secured to a substrate 124 which is mounted in the recess120 by appropriate means. The drive circuit 122 is operatively connectedto the piezoelectric film sensor 110 through terminals 126. Electricalwires 128 connect the drive circuit 122 to the controller 36.

The piezoelectric film sensor 110 is a multi-layer structure including afirst piezoelectric layer 130 and a second piezoelectric layer 136separated by an insulating layer 138. The two piezoelectric layers andthe insulating layer are secured together in an integral assembly byappropriate means. Each layer 130, 136 has an associated electrodesilk-screened on each side of the layer. The electrodes of eachpiezoelectric layer 130, 136, is connected to an associated terminal126. Specifically, the top electrode for layer 130 is connected toterminal 126'. The bottom electrode for layer 130 is connected toterminal 126". The top electrode for layer 136 is connected to terminal126". The bottom electrode for layer 136 is connected to terminal 126"'.

When energized by the film drive circuit 122, portions of thepiezoelectric layers, under their associated electrodes, flex. The drivecircuit 122 is adapted so that the piezoelectric film sensor 110oscillates. The film oscillation physically occurs over the recessedportion 112 of the bottom plate 92. This area of the film sensor 110 isreferred to as the bridge.

The upper plate 94 includes an contact arm 140 that extends normal tothe plate 94 and the surface 98 toward the film sensor 110. The upperplate 94 is made from a flexible material. When an occupant sits on theseat cushion 42, his weight is transferred through the material thatmakes up the seat cushion to the upper plate 94. The force applied tothe upper plate 94 is functionally related to the occupant's weight.Since the bottom plate 92 is rigidly secured relative to the vehiclefloor, the upper plate 94 flexes in response to the occupant's weighttransferred through the seat material. As the upper plate 94 flexes, thecontact arm 140 moves toward the layers 130, 136 of film sensor 110.

When no occupant is sitting on the seat cushion and the film layers areenergized by the film drive circuit 122, the film oscillates. When thefilm oscillates, the output of the drive circuit oscillates with acertain peak-to-peak voltage value. If an occupant who has a weightgreater than a predetermined weight then sits on the seat cushion, theupper plate 94 flexes an amount sufficient to insure that the contactarm 140 contacts the film 110. If the arm 140 contacts the film 110, theoscillations of the film 110 are attenuated. The resultant output fromthe film is a DC voltage value equal to approximately one-half thepeak-to-peak voltage when no occupant is sitting on the seat cushion. Bymonitoring the output of the film 110, the controller is provided withan indication as to whether an occupant is located on the seat cushion60.

FIGS. 5, 6 and 7, show a processing circuit, made in accordance with oneembodiment of the present invention. In this embodiment, the occupantsensor is the sensor 60. The sensor 60 is used to determine whether anoccupant is sitting on the seat cushion 42. The controller 36 monitorsthe output signal from the sensor 60. The controller 36 enablesactuation of the airbag when either the signal from the sensor 60indicates that an occupant is sitting in the seat or the absence of asignal from the sensor 60 indicates that an electrical fault conditionexists such as an open or short circuit between the sensor 60 and thecontroller 36.

FIG. 6 shows the drive circuit 122 in detail. The top electrode ofpiezoelectric layer 130 is connected through terminal 126 to theinverting input of an op amp 144, connected as a differentiator, througha resistor. The differentiator with op amp 144 has a feedback resistor145. The output of the op amp 144 is connected to the inverting input ofan op amp 142, connected as an amplifier, through an input resistor 147.The amplifier 142 includes a feedback resistor 143. The output of theamplifier is connected to the bottom electrode of piezoelectric layer136 through terminal 126"'. The bottom electrode of piezoelectric layer130 and the top electrode of piezoelectric layer 136 are connected to asource of electrical energy -V_(cc) through terminal 126". Thenoninverting inputs for the amplifiers 142, 144 are connected to acommon ground having a voltage value between +V_(cc) and -V_(cc)established through a resistor divider network 149 with equal valueresistors. If the vehicle battery is used as the source of electricalenergy, -V_(cc) is ground of the battery, and +V_(cc) is the positive 12VDC of the battery. Therefore, the common ground of the circuit 122 isat +6 VDC.

The layers 130 and 136 have a predetermined amount of capacitance acrosstheir associated terminals. The layers 130, 136 have a capacitance of1.5 nanofarads. The amplifier 142 with resistors 143, 147 has anextremely large gain. Because the amplifier 142 has a greater than 0 dbgain at 180 degree phase shift, the output 148 of the amplifier 142 willoscillate at a frequency equal to: ##EQU1## where R is the value ofresistor 145 and C is the series connected value of the capacitances ofthe layers 130, 136. In the example given, the series capacitance is0.75 nanofarads. In a preferred embodiment of the present invention, anoutput voltage is provided at a terminal 148 having a frequency ofapproximately 2 kilohertz. It should be noted that the continuousoscillations at the output of the film drive circuit 122 are dependentupon the freedom of the layers in the film 110 to move.

Because the capacitance values of the piezoelectric layers are used ascomponent values in the drive circuit 122, the circuit must be placed inclose proximity to the piezoelectric film 110 to avoid line capacitancethat would occur in long lead lines. The drive circuit 122 is placedupon the substrate 124 so as to be close to the film 110.

The output 148 is connected to the input of the controller 36. Thecontroller 36 includes a bandpass filter 150, of standard design wellknown in the art, connected to the output 148 of the film drive circuit122. The bandpass filter 150 is designed, in accordance with a preferredembodiment of the present invention, to pass frequencies of 2 kilohertz.The bandpass filter 150 may be external to the sensor 60 or can beplaced upon the substrate 124 along with the drive circuit. As shown inFIG. 8, the output 152 of the bandpass filter is an oscillating voltagebetween zero volts DC (battery ground) and a voltage value V+ (thepositive battery terminal) at a frequency of 2 kilohertz. The timeperiod P between pulses is equal to 0.5 msec., which is one divided bythe frequency of 2 kilohertz. The line 154 shown in FIG. 8 representsforce or stress against the top plate 94 of the sensor 60 as a result ofan occupant sitting on the seat cushion 62. At time t₁, the occupant'sweight deflects the top plate 94 a sufficient amount so that the contactarm 140 contacts the film 110. When contact occurs between the arm 140and the film 110, the output of the bandpass filter changes to a DCvoltage equal to approximately one-half V+, as shown by the line 168.The voltage goes to one-half V+ because the common ground of circuits122, 150 is at one-half V+. Specifically, V+ is the positive terminal ofthe vehicle battery and chassis ground is the negative terminal of thevehicle battery. Common ground for the drive circuit 122 and the bandpass filter 150 is at one-half the value of the battery voltage as isshown in FIG. 6. Therefore, when the oscillations of the piezoelectriclayers stop, the output of the band pass filter and the drive circuit goto their common ground value, which is one-half V+, i.e., 6 VDC.

A counter 158, also part of the controller 50, is connected to theoutput 152 of the bandpass filter 150 and counts the output pulses fromthe bandpass filter. The output of the counter 158 is connected to afirst input 159 of a digital comparator 160. The second input 161 of thedigital comparator 160 is connected to a hard wired count in digitalform designated by 162 in FIG. 5.

The counter is wired to be periodically reset by a reset circuit 163.The reset circuit 163 includes a clock 164 connected to a reset input ofthe counter 158 through a delay circuit. The delay circuit includes twoinverters 165, 166 and a delay capacitor 167 connected to the output ofthe inverter 166. The output of the clock 164 is further connected tothe strobe input of the digital comparator 160.

The clock outputs a periodic pulse. For the purpose of explanation only,the pulse occurs once per second. Also, assume the count from the hardwired count is 2,000. The clock outputs a HIGH signal for the strobe andthe reset of the counter 158. The delay circuit insures that the countfrom the counter is strobed into the digital comparator prior to thereset of the counter 158. If the counter 158 is reset once a second, thecounter output at the end of that one second, i.e., just prior to reset,will be equal to a count of 2,000.

The output of the digital comparator 160 has three outputs including anoutput 170 which changes states based on the input of the counter 158.If no occupant is sitting on the seat cushion 42, the output of thecounter 158 will be a count value of 2,000. When this occurs, the output170 is a digital HIGH. A digital HIGH at the output 170 therebyindicates no occupant is on the seat cushion. If an occupant sits on theseat cushion 42 so that the arm 140 contacts the film 110, the output ofthe band pass filter 150 assumes a DC value, and the counter 158 countszero pulses. The output 170 of the digital comparator 160 then goes to adigital LOW.

If an electrical fault such as an open or short circuit occurs in thesensor 60, the output 148 will go to a DC voltage value equal to eitherzero volts DC (the battery ground) or V+ (the positive battery terminal)because input noise will result in saturation of one of the op amps 142,144. In either case, the counter will count zero pulses when anelectrical fault occurs between the sensor 60 and the controller 50.Therefore, if an electrical fault occurs between the sensor 60 and thecontroller 36, the output 170 goes to a digital LOW.

It should be appreciated that the output 170 of the digital comparator160 will be a digital HIGH only when (i) an occupant is not sitting onthe cushion 42, (ii) the sensor film is properly operating, i.e., thesensor film is oscillating at 2 kilohertz, and (iii) all electricalwires are connected from the sensor film up to the digital comparator160. Otherwise, the output 170 will be at a digital LOW.

The output 170 of the digital comparator 160 is connected to the inputof an inverter 172. The output of the inverter 172 is connected to afirst input of an AND gate 174. The second input of the AND gate 175 isconnected to the output of a read-only memory 180 in the controller 36.The read-only memory 180 is connected to the output of the crash sensoraccelerometer 38. A control algorithm is programmed in the read-onlymemory 180 to process the output of the accelerometer 38. The controlalgorithm can take any of several forms. For example, if theaccelerometer is of the type that provides a linear electric signalindicative of sensed deceleration (crash condition), the controlalgorithm may integrate the accelerometer signal. Once the integralreaches a predetermined value indicative of a crash condition, thealgorithm provides a digital HIGH to the AND gate 174. Thus, thecontroller, as a result of the algorithm 180, provides a digital HIGHsignal when the signal from the accelerometer indicates that the vehicleis in a crash condition.

The output of the AND gate 174 is a digital HIGH when a crash conditionoccurs and either (i) an occupant is sitting on the seat cushion 42 or(ii) an electrical fault exists between the sensor 60 and the controller36 so that, in either case, the output of the inverter 172 is a digitalHIGH. In all other situations, the output of the AND gate 174 is adigital LOW.

The output of the AND gate 174 is connected to an input of an OR gate183. The read-only memory 180 is connected to the other input of the ORgate 183 on line 185. The read-only memory also includes a controlalgorithm that determines the speed of the crash. Preferably, this isaccomplished by monitoring the slope of an integration curve. If thespeed of the crash exceeds a predetermined value, the control algorithmprovides a digital HIGH on line 185. If the speed of the crash isgreater than a predetermined value or the output of AND gate 174 is adigital HIGH, the output of OR gate 183 is switched to a digital HIGH.The output of OR gate 183 is connected to a drive circuit 184. Theoutput of the drive circuit 184 is connected to an electric switch 186,such as a field-effect transistor ("FET"). The FET 186 is connected inseries with the squib 40 across a source of electrical energy. The drivecircuit 184 turns the FET 186 ON when the output of the OR gate 183 is adigital HIGH. Turning the FET ON ignites the squib 54 which, in turn,actuates the gas source 32 and inflates the airbag 26. It should beunderstood that the controller 36 enables deployment of the airbag 26upon the detection of both a vehicle crash condition (with crash speedless than the predetermined value) and either the presence of anoccupant on the seat cushion 42 or the occurrence of an electrical opencircuit between the film sensor 60 and the controller. Also, if thespeed of the crash is greater than the predetermined value, the airbagis deployed by the control algorithm 180 and OR gate 183 independent ofwhether an occupant is present on the seat.

An error detect circuit 188, which is part of the controller 36, isconnected to the output 148 of the film drive circuit 122. An output 190from the digital comparator is connected to an enable input of the errordetect circuit 188. Whenever an occupant is sitting on the seat cushion42 or an electrical fault occurs between the sensor 60 and thecontroller 36, the output 190 of the digital comparator 160 is a digitalHIGH. In other words, when output 170 is LOW, output 190 is HIGH. Whenthe output 190 is HIGH, the error detect circuit 188 is enabled. Whenenabled, the error detect circuit monitors the output voltage at theoutput 148 from the film drive circuit 122. If the voltage present onthe output 148 is outside of a predetermined window centered at one-halfV+, an error indicator 192 located in the dash board 24 is energized towarn the vehicle operator. The voltage on output 148 being outside ofthe window at one-half V+ indicates that an electrical fault hasoccurred. If the output 148 is within the window at one-half V+, plus orminus a predetermined value, such condition indicates that an occupantis sitting on the seat cushion 42.

FIG. 9 shows an occupant restraint system 220 made in accordance withanother embodiment of the present invention. The occupant restraintsystem 220 includes an airbag assembly 222 mounted in an opening of adashboard 224 of a vehicle. The airbag assembly 222 includes an airbag226 folded within the interior of an airbag housing 228. A cover 230covers the airbag and is adapted to open easily upon the inflation ofthe airbag 226.

Two sources 232, 233 of inert gas are mounted at the back of the housing228 and are operatively connected to the airbag 226. The gas sources232, 233 may be containers of combustible gas generating material orpressurized gas. The gas sources 232, 233 are actuated by electricalsquibs or initiators 254, 255. Gases discharged by actuation of the gassources 232, 233 fills the airbag 226 to its inflated condition 226'.Once inflated, as occurs during a vehicle crash, the airbag 226 cushionsan occupant located in a vehicle seat 234.

A vent valve 238 is operatively connected to the gas sources 232.Similarly, a vent valve 239 is operatively connected to the gas source233. The vent valves 238, 239 are used to control the inflation of theairbag 226. If the vent valves 238, 239 are fully closed upon actuationof the gas sources 232, 233, the airbag 226 inflates to its maximumvolume, at maximum pressure and maximum inflation rate. By controllingwhether one or both gas sources are actuated and by controlling thedegree to which the vent valves 238, 239 are opened, the inflation rateand pressure of the airbag are controlled to values less than themaximum values.

Electric motors 240, 242 are operatively connected to the housing 228 ofthe airbag assembly 222. The motor 240 is operatively connected to thehousing 228 so as to control movement of the airbag assembly 222angularly about a vertical axis 244 leftward or rightward, shown byarrow 245, as viewed by the occupant sitting in seat 234. The motor 242is operatively connected to the housing 228 so as to move the airbagassembly 222 angularly about a horizontal axis 246 (normal to FIG. 9)upward or downward, shown by arrow 247, as viewed from the seat 234. Themotors 240, 242 are used to control the orientation of the airbagassembly 222 relative to an occupant sitting in the seat 234.

An electronic controller 250, such as a microcomputer, is operativelyconnected to a vehicle crash sensor 252. The crash sensor 252 can be anyof several known types. For example, the crash sensor 252 may be amechanical inertia switch, such as a rolamite sensor, or an electricalaccelerometer that provides an oscillating output signal indicative ofwhether the vehicle is in a crash condition. If a normally open inertiaswitch closes, this is an indication that a crash is occurring.Likewise, if the signal from an electrical accelerometer reaches apredetermined level or a predetermined level for a predetermined time,this is an indication that a crash is occurring.

Once the controller 250 determines that a vehicle crash is occurring forwhich deployment of the airbag is necessary to protect the vehicleoccupants, the controller 250 ignites at least one of the squibs 254,255 which, in turn, respectively actuates one or both of the associatedgas sources 232, 233. The controller 250 is also electrically connectedto the vent valves 238, 239 and controls the amount of gas bled off fromthe gas sources 232, 233 during inflation of the airbag 226. By bleedingoff a certain amount of gas from the gas sources, the speed ofdeployment, the size, and pressure of the airbag 226 are controlled.

The occupant seat 234 with which the occupant restraint system 220 isused is preferably a passenger seat in the vehicle. The seat 234includes an occupant position and weight sensor 260 located in thebottom cushion 262 of the seat 234. A humanistic sensor 264 is locatednear the top of the cushion 262. An occupant sensor 266 is located inthe back cushion 268 of the seat 234.

The occupant position and weight sensor 260 detects (i) if an object ispresent on the seat, (ii) the weight of the object, and (iii) theposition of the object in the seat. The humanistic sensor 264 detectswhether an object on the seat cushion 262 is animate or inanimate. Theoccupant sensor 266 detects whether an object is contacting the backcushion 268.

In addition to the sensors 260, 264 and 266, a seat back incline sensor270 is operatively connected between the lower cushion 262 and the uppercushion 268. The sensor 270 provides an electrical signal indicative ofthe angular displacement of the seat back cushion 268 relative to thevehicle floor. Preferably, the seat back incline sensor 270 is a rotarypotentiometer. A seat position sensor 272 is operatively connected tothe lower cushion 262 and a sliding rail 274 upon which the seat 234 isslidably mounted in a manner well known in the art. The sensor 272provides an electrical signal indicative of the forward and backwardposition of the seat 234 relative to a predetermined reference point.Preferably, the seat position sensor 272 is a linear potentiometer.Based on the signal from the sensor 272, the distance from the frontcover 230 to the seat back 268 can be determined.

The sensors 260, 264, 266, 270 and 272 are collectively referred to asthe seat and occupant sensors 280. The seat and occupant sensors 280 areelectrically connected to the controller 250. Based upon (i) thepresence or absence of an object on the seat, as indicated by the sensor260, and (ii) whether the object is animate from the sensor 264, thecontroller 250 determines whether or not to enable the airbag assembly222. Based upon (i) the sensed position of the seat 234 from sensor 272,(ii) the incline of the seat from sensor 270, (iii) the weight of theoccupant from sensor 260, and (iv) the position of the occupant in theseat from sensors 260 and 266, the controller 250 controls the inflationrate, size, pressure, deployment orientation and deployment timing ofthe airbag 226. The controller 250 controls deployment orientationthrough a motor control drive circuit 282 operatively connected to theairbag position motors 240, 242.

Referring to FIGS. 10-12, the occupant position and weight sensor 260includes an N×M array of individual position sensors 300 and individualweight sensors 302. FIG. 10 shows a specific arrangement of sensors 300,302. The array shown is an 8×8 array with the position and weightsensors alternately positioned in the array in a checkerboard pattern.It should be appreciated that the invention is neither limited to thisspecific array nor pattern of sensors.

The sensors 300 are all identical in structure to the sensor 60described with regard to FIGS. 2, 3, and 4. Each sensor 300 has its ownmultilayer piezoelectric film 308 and a drive circuit 304 mounted nextto the film on an associated substrate 306. Each drive circuit 304 isidentical to the drive circuit shown in FIG. 6 with regard to the sensor60. The output of each drive circuit 304 is connected to the controller250. Each film 308 is mounted across an associated recess 310 in abottom support plate 312 that provides the recesses for all of thefilms. A top plate 314 which covers all of the films 308 and drivecircuits 304 is secured to the bottom plate 312 by screws as describedwith regard to sensor 60. An annular gasket 316 is interposed betweenthe top plate 314 and the bottom plate 312. The gasket 316, top plate314, and bottom plate 312 form a chamber 318.

The top plate has a plurality of contact arms 320 extending downwardtoward the bottom plate 312. Each sensor 300 has an associated contactarm 320 located over its film 308. The top plate 314 is made from amaterial that flexes in response to a force or load. The amount offlexure at any point on the upper plate 314 is a function of the weightof the occupant at the corresponding location on the seat cushion 262.When a contact arm 320 contacts its associated film 308, the outputsignal from the associated drive circuit 304 changes in the same mannershown in FIG. 8 with regard to sensor 60. By monitoring which sensors300 indicate the presence of an object, the position of the object inthe seat 234 can be determined. Based upon this determined position, thecontroller 250 can control the orientation of the airbag assembly 222and the time at which the airbag is deployed. As described with regardto sensor 60, sensors 300 also provide an indication of an electricalfault condition in the sensors such as an open circuit and a short toground.

Each of the sensors 302 includes a force sensing film 330 mounted acrossan associated recess 332 in the bottom plate 312. The force sensingfilm, which is also referred to herein as weight sensing film, is aforce sensing resistor ("FSR") film. This type of film has apredetermined amount of resistance seen across its connection terminals.The resistance across the terminals varies inversely with applied force.Like the sensors 300, each sensor 302 has an associated contact arm 334located above the film and extending downward from the top plate 314.Each sensor 302 also has an associated drive circuit 336.

As previously mentioned, the top plate 314 is made from a material thatflexes in response to an applied load or force. The amount of flexure atany point on the upper plate 314 is a function of the weight of theoccupant at the corresponding location on the seat cushion 262. When acontact arm 334 contacts its associated film 330, the output signal fromthe associated drive circuit 336 varies as a function of the occupant'sweight at that location. By monitoring the sensors 302, the weight ofthe occupant on the seat 234 can be determined. Based upon thisdetermined weight, the controller 250 can control deployment of theairbag.

The sensors 300, 302 are designed so that a predetermined amount ofweight must first be applied to the seat cushion before the arms 320,334 contact their associated films 308, 330. For example, it iscontemplated that twenty pounds would have to be placed upon the seatcushion 262 before the arms 320, 334 would contact their associatedfilms 308, 330. For each force or weight sensor 302, any change inresistance will be functionally related to the weight of the occupant.FIG. 14 is a graph depicting the impedance of the sensor film 330. Whenno weight is on the seat cushion 262, the impedance of the film is quitehigh. As the weight increases, the impedance decreases. The graph showsthe occupant sitting on the seat at time t₁.

For purposes of designing and evaluating occupant restraint systems,industrial standards have been established to model, on a theoreticalbasis, the population as a whole. These standards define theoreticalindividuals in terms of overall weight, height, torso length, andvarious other anatomical characteristics. Based on actual measurementsof one of these characteristics, such as weight, other characteristicsof a vehicle occupant can be assumed, with a predetermined statisticalprobability of correctness, from the industrial standards. FIG. 15, forexample, correlates changes in resistance of the film 330 to weights oftheoretical males in these industrial standards. For example, a 95thpercentile (denominated 95% in FIG. 15) male weighs 220 lbs., a 50thpercentile male weighs 165 lbs., and a 3 year old child weighs 30 lbs.The controller 250 controls the deployment of the airbag 226 based onthe change in resistance of the film 330 and the computed weight of theoccupant. Depending upon the weight of the occupant and his relatedtheoretical anatomical dimensions, the airbag 26 is deployed in a crashcondition at a time after the onset of a crash which is derived from,preferably, a look-up table. Data stored in the look-up table is derivedfrom historical data and/or empirical testing. The detected weight ofthe occupant is also used by the controller 250, together with theposition of the occupant, to control the vent valves 238, 239. FIG. 16is a multipurpose depiction of the control of the vent valves 238, 239.First, FIG. 16 depicts a percent of the gas dumped through the ventvalves as a function of the determined weight of the occupant. Thelighter the occupant sitting in the seat 234, the larger the percentageof gas from the gas sources 232, 233 which should be diverted away fromthe airbag 226 and dumped. Second, FIG. 16 depicts a percent of gasdumped through the vent valves as a function of the position of theoccupant in the seat. The closer the occupant is to the cover 230, thelarger the percentage of gas that should be dumped from the gas sources232, 233. The amount of gas dump required for weight and distance arebased from historical data including empirically determined data.

The controller 250 further uses the occupant's weight to control whetherone or both squibs are fired during a vehicle crash requiring deploymentof the airbag. For example, if the occupant weight is determined to beless than a 50th percentile person, only one of the squibs 232, 233 maybe fired. If the occupant weight is determined to be greater than a 50thpercentile person, both of the squibs may be fired.

The controller 250 monitors the distance between the occupant and thefront cover 230 of the airbag assembly 222. This distance is determinedby knowing the position of the seat 234 from the seat position sensor272, the incline of the seat back from the sensor 270, and the positionof the occupant in the seat 234 based upon the output signals fromsensors 260 and 266. A determination is made as to whether the occupantis at a location relative to the airbag assembly for which the airbagwould not provide effective protection in a crash condition. If it isdetermined that an occupant is sitting at this ineffective protectionlocation, the airbag is not deployed upon a vehicle crash condition. Thecontrol of firing one or two squibs can also be controlled in responseto the sensed position of the occupant.

FIGS. 17 and 18 graphically depict orientation or aiming control for theairbag assembly 222 left/right and up/down, respectively. If it isdetermined that the occupant is sitting in the left portion of the seatfrom the position sensors 300, the airbag assembly 222 is rotated to theleft. If it is determined that the occupant is sitting in the rightportion of the seat from the position sensors 300, the airbag assembly222 is rotated to the right. If it is determined that the occupant issitting in the front portion of the seat from the position sensors 300,the airbag assembly 222 is rotated upward. If it is determined that theoccupant is sitting in the back portion of the seat from the positionsensors 300, the airbag assembly 222 is rotated downward.

The aiming or orientation of the airbag assembly 222 is controlledthrough the motor drive control 282. The motor drive control 282 is astepper motor controller with the motors 240, 242 preferably beingstepper motors. The controller 250 outputs a horizontal positioncontrol, including a horizontal step input and a direction enable input.The controller 250 outputs a vertical position control, including avertical step input and a direction enable input. Based upon these inputsignals from the controller 250, the motor controller 282 outputs theappropriate drive signals to the motors 240, 242 in a manner well knownin the art.

The sensor 264 in the seat cushion 262 is a piezoelectric film of thetype that detects infrared energy. When an occupant sits in the seat234, he gives off infrared energy which is sensed by the sensor 264.This sensor then provides a signal indicative of whether the object inthe seat 234 is animate or inanimate. The sensor 264 is connected to thecontroller 250. If, during a crash condition, an inanimate object is onthe seat cushion, the airbag 226 is not deployed.

FIG. 19 depicts the output from the sensor 264. The output from theinfrared sensor is a voltage having a value indicative of the change intemperature to which it is subjected. When the controller 250 monitors alarge voltage from the sensor 264, such indicates that an animate objectis sitting in the seat. The graph depicts an occupant sitting on theseat at time t₁.

The seat back sensor 266 is preferably a piezoelectric sensor identicalin structure to the sensors 60 and 300 and can either be a single sensoror an array. The sensor 266 is connected to the controller 250 andprovides an indication as to whether the occupant is seated all the wayback in the seat 262. The contact arm for the sensor 266 is located muchcloser to its associated film layer so that only a small amount of forceis required against the back of the seat to effect a change in thecondition of the electrical characteristic of the film.

Referring to FIG. 12, the controller 250, in this array embodiment, ispreferably a microcomputer separately connected to the output of each ofthe sensors 300, 302, 270, 272, 264 and 266. The outputs of themicrocomputer are connected to the individual squibs 254, 255. Themicrocomputer's outputs are also connected to the vent valves 238 and239, as well as the motor drive control 282.

FIGS. 20-22 provide a flow chart for the control process followed by thecontroller 250. In step 400 the controller 250 is initialized by settingnumbers used in the process to zero, resetting flags where applicable,initially enabling the airbag, and initially aiming the airbag to amiddle position. In step 402, the sensor outputs are scanned by themicrocontroller. In step 404, a determination is made as to whether anobject is present in the seat. For the embodiment shown in FIG. 9, anyof the sensors 300, 302, or 264 can be used to determine if an occupantis present. The sensors 300, 302 and 264 provide an indication ofwhether an object is in the seat independent of whether the object isanimate or inanimate.

If the determination in step 404 is negative, the process proceeds tostep 406 where a value N is set equal to N+1. The process proceeds tostep 408 where a determination is made as to whether N is equal to 10.The first determination in step 408 is negative since N was set equal tozero in step 400. The process then loops back to step 402. After 10times through steps 402, 404, 408, the determination in step 408 isaffirmative. When the determination in step 408 is affirmative, theprocess proceeds to step 410 where the airbag is disabled. The processthen loops back to step 402.

If the determination in step 404 is affirmative, the process proceeds tostep 412 where a determination is made as to whether or not the objectin the seat is a human. This is done by monitoring the output of thesensor 264. If the determination in step 412 is negative, the processproceeds to step 414 where the airbag is disabled.

If the determination in step 412 is affirmative, the process proceeds to"step" 416 where the airbag is kept in an enabled condition. This "step"is non-functional and is shown in the flow chart as a reminder that theairbag is maintained enabled at this point in the process. The processproceeds to step 418 where the controller 250 determines which of thesensors 300 in the array 260 are ON. The position of the occupant isthen determined in step 420 from the ON sensors in the array 260.

A determination is then made in step 422 as to whether the occupant inthe seat is out of position. Out of position means that the occupant isin a position for which the airbag can not provide effective protectionduring a crash condition. If the determination in step 422 isaffirmative, the process proceeds to step 424 where the airbag isdisabled.

If the determination is step 422 is negative, which means that theoccupant is located in the seat 234 in a location in which the airbagwould provide effective crash protection, the process proceeds to step450 (FIG. 21) where a determination is made as to whether the occupantis sitting in the back middle of the seat. If the determination in step450 is affirmative, the process proceeds to step 452 where the weight ofthe occupant is determined. By the occupant being in the back middle ofthe seat 234, the airbag does not need further aiming since it was setto a middle position in step 400.

If the determination in step 450 is negative, the process proceeds tostep 454 where a determination is made as to whether the occupant issitting in the front middle of the seat. If the determination in step454 is affirmative, the process proceeds to step 456 where the airbagassembly 222 is rotated down toward the floor. The process then proceedsto step 452. If the determination in step 470 is negative, the processreturns to step 450.

If the determination in step 454 is negative, the process proceeds tostep 458 where a determination is made as to whether the occupant issitting in the front left of the seat. If the determination in step 458is affirmative, the process proceeds to step 460 where the airbagassembly 222 is rotated down and to the left. The process then proceedsto step 452.

If the determination in step 458 is negative, the process proceeds tostep 462 where a determination is made as to whether the occupant issitting in the front right of the seat. If the determination in step 462is affirmative, the process proceeds to step 464 where the airbagassembly 222 is rotated down and to the right. The process then proceedsto step 452.

If the determination in step 462 is negative, the process proceeds tostep 466 where a determination is made as to whether the occupant issitting in the back left of the seat. If the determination in step 466is affirmative, the process proceeds to step 468 where the airbagassembly 222 is rotated up and to the left. The process then proceeds tostep 452.

If the determination in step 466 is negative, the process proceeds tostep 470 where a determination is made as to whether the occupant issitting in the back right of the seat. If the determination in step 470is affirmative, the process proceeds to step 472 where the airbagassembly 222 is rotated up and to the right. The process then proceedsto step 452. If the process in step 470 is negative, the process returnsto step 450.

After the position of the occupant is determined from the processdepicted in FIG. 21, the process proceeds to step 452 where theoccupant's weight is determined. The process proceeds to step 480 wherea determination is made, based on the occupant's weight, as to whetherthe occupant is approximately the size of a theoretical 3 year old. Thisdetermination, as well as the other weight-based determinationsdescribed hereafter, will be based on the determined weight of theoccupant being within a range of weights, rather equal to a specificweight. If the determination is affirmative, the process proceeds tostep 482 where 75% of all gas discharged by one gas source is dumped viaits associated vent valve. The other gas source is not actuated. From anegative determination in step 480, the process proceeds to step 484.

In step 484, a determination is made as to whether the occupant is thesize of a 5th percentile person. If the determination is affirmative,the process proceeds to step 486 where 50% of all gas discharged by onegas source is dumped via its associated vent valve. The other gas sourceis not actuated. From a negative determination in step 484, the processproceeds to step 488.

In step 488, a determination is made as to whether the occupant is thesize of a 25th percentile person. If the determination is affirmative,the process proceeds to step 490 where 25% of all gas discharged by onegas source is dumped via its associated vent valve. The other gas sourceis not actuated. From a negative determination in step 488, the processproceeds to step 492.

In step 492, a determination is made as to whether the occupant is thesize of a 50th percentile person. If the determination is affirmative,the process proceeds to step 494 where the gas discharged by one gassource is not dumped at all. The other gas source is not actuated. Anyweight detected greater than a 50th percentile person results inactuation of the second gas source. From a negative determination instep 492, the process proceeds to step 496.

In step 496, a determination is made as to whether the occupant is thesize of a 75th percentile person. If the determination is affirmative,the process proceeds to step 498 where 50% of the gas discharged by thesecond gas source is dumped via its associated vent valve. From anegative determination in step 492, the process proceeds to step 500.

In step 500, a determination is made as to whether the occupant is thesize of a 90th percentile person. If the determination is affirmative,the process proceeds to step 502 where 25% of the gas discharged by thesecond gas source is dumped via its associated vent valve. From anegative determination in step 500, the process proceeds to step 504.

In step 504, a determination is made as to whether the occupant is thesize of a 99th percentile person. If the determination is negative, theprocess loops back to step 480. If the determination is affirmative, theprocess proceeds to step 506 where no gas is dumped from either of thegas sources. From any of the steps 482, 486, 490, 494, 498, 502, or 506,the process proceeds back to step 510 which is a determination of theoccupant's position shown in FIG. 21.

It should be appreciated that the various steps for weight and positiondetermination can occur in any order. Also, the weight determinationsand vent valve adjustments can be made in smaller increments, ifdesired. Further, the occupant's position can be determined and then theprocess would branch to the appropriate action based upon thatdetermined position. Similarly, the occupant's weight can be determinedand the process would branch to the appropriate action based upon thatdetermined weight.

FIG. 23 shows another embodiment of the present invention. In thisembodiment, a plurality of piezoelectric film sensors 550 are secured toa rubber pad 540 and provide an electric pulse when deflected due to theweight of the occupant on the seat cushion. By monitoring which films550 provide an electric pulse, position of the occupant can bedetermined. Weight sensors 560 are also secured to the rubber pad 540and provide an indication of the occupant weight which is functionallyrelated to the amount of film flexure. The position sensors 550 andweight sensors 560 are located on the rubber pad in a checker-boardpattern as described above. The rubber pad is located in the seatcushion at a location which permits flexure of the pad in response toweight and position of the occupant. The controller in this embodimentprocesses the signals from the weight film sensors in the same manner asdescribed above. The controller monitors the seat position sensors anddetermines the occupant's position in response to which position filmsprovide a pulse output. The airbag deployment and direction arecontrolled as described above.

From the above description of a preferred embodiment of the invention,those skilled in the art will perceive improvements, changes andmodifications. Such improvements, changes and modifications within theskill of the art are intended to be covered by the appended claims.

Having described a preferred embodiment of the invention, the followingis claimed:
 1. An occupant sensing apparatus for use in an occupantrestraint system, comprising:a plurality of sensing elements located inan occupant seat and arranged in N×M rows and columns forming an array,each sensing element being made from a film having an electricalcharacteristic having a changeable state upon flexure of said film,wherein selected ones of said sensors provide an indication of occupantweight; a plurality of contacting means, each of said sensing elementsof said array having an associated contacting means for effectingflexure of said sensing element in response to contact between saidcontacting means and said sensing element; means for moving at leastsome of said contacting means into contact with their associated sensingelement when an occupant sits on said occupant seat; and controllermeans connected to each of said sensing elements of said array foranalyzing said electrical characteristic states of said sensing elementsand determining position and weight of said occupant from said analysis,said control means further including means for controlling actuation ofsaid occupant restraint system in response to the determined positionand weight of said occupant.
 2. The occupant sensing apparatus of claim1 wherein certain said films are a piezoelectric film.
 3. An occupantposition and weight sensor for use in an occupant restraint system,comprising:a plurality of sensing elements located in an occupant seatand arranged in N×M rows and columns forming an array, each sensingelement incorporating one of two types of film having an electricalcharacteristic with changeable states upon flexure of said film, a firstfilm functioning as an occupant position sensor and a second filmfunctioning as a weight sensor; a plurality of contacting means, each ofsaid sensing elements of said array having an associated contactingmeans for effecting flexure of said film of its associated sensingelement in response to contact between said contacting means and saidfilm of its associated sensing element; means for moving at least someof said contacting means when an occupant sits on said occupant seat;means for mounting said films in occupant seat; and controller meansconnected to each of said sensing elements for analyzing said electricalcharacteristic of said films and providing a disable signal when saidstates of said electrical characteristics of said films in said sensingelements indicates no occupant is present and providing an enable signalwhen either (i) said states of electrical characteristics indicates anoccupant is present or (ii) said states of said electricalcharacteristic indicates that an electrical fault condition exists inany of said sensing elements, said controller means further includingmeans for determining position and weight of an occupant from saidsensing elements, said controller controlling actuation of said occupantrestraint system in response to the determined position and weight ofsuch occupant.
 4. The occupant position and weight sensor of claim 3wherein said first film elements are piezoelectric film and said secondfilm element are force sensing resistance film, wherein said controlmeans includes means for driving each piezoelectric film intooscillation, contact between a contacting means and an associatedpiezoelectric film attenuating said oscillations, said control meansmonitoring said oscillations of said film.
 5. An occupant positionsensor for use in an occupant restraint system, comprising:a pluralityof sensing elements located in an occupant seat and arranged in N×M rowsand columns forming an array, each sensing element incorporating one oftwo types of film, a first film functioning as an occupant positionsensor and a second film functioning as a weight sensor; a plurality ofcontacting means, each of said sensing elements of said array having anassociated contacting means for effecting flexure of said film of anassociated sensing element in response to contact between saidcontacting means and said film of said associated sensing element; meansfor moving at least some of said contacting means into contact with itsassociated film when an occupant sits on said occupant seat; means formounting said films, each of said contacting means including a contactmember, each said contact member being in said occupant seat so that thepresence of an occupant upon said seat effects physical contact betweencertain of said contact members and their associated film of itsassociated sensor elements, contact between said contact member and itsassociated film effecting a change in a state of said electricalcharacteristic associated with each of said sensor elements, certain ofsaid sensor elements having an electrical characteristic with a firststate when there is no occupant present and no contact between saidcontact member and said certain of said sensor elements, and having asecond state when there is an occupant present and contact between saidcontact member and said certain of said sensing elements; controllermeans connected to each of said sensing elements for analyzing saidstates of said sensing elements and providing a disable signal when saidstates indicate no occupant is present, and an enable signal when either(i) said states indicate an occupant is present, and (ii) said statesindicate an electrical fault condition in any of said sensor elementssaid array; and said controller means further includes means fordetermining position and weight of an occupant from said sensingelements and controls actuation of said occupant restraint system inresponse to the determined position and weight of such occupant.
 6. Anoccupant restraint system for a vehicle comprising:an airbag assemblymovably mounted in a dashboard of the vehicle, said airbag assemblyincluding an airbag; means for moving said airbag assembly upward,downward, rightward, and leftward relative to an occupant seat; N×M rowsand columns forming an array of position and weight sensors mounted inthe occupant seat, said array including a plurality of contacting means,each of said sensors of said array having an associated contacting meansfor effecting flexure of an associated sensor in response to a forceapplied by said contacting means, certain of said contacting meanscontacting their associated sensor when an occupant sits on the vehicleseat, said array providing an indication of an occupant's leftward,rightward, forward, and backward position in the seat and an occupant'sweight; crash sensor means for providing a signal upon occurrence of avehicle crash; and control means connected to said airbag assembly, saidmoving means, said array, and said crash sensor for (i) controlling theposition of the airbag assembly in response to the sensed position ofthe occupant and (ii) controlling deployment of the airbag in responseto the signal from said crash sensor and both the sensed position andweight of the occupant.
 7. The system of claim 6 further including aninfrared sensor for providing an indication to said control means as towhether an object in the seat is an animate or inanimate object, saidcontrol means disabling deployment of said airbag if the object isdetermined to be inanimate.
 8. The system of claim 6 wherein saidposition sensors are made from piezoelectric film.
 9. The system ofclaim 6 wherein said weight sensors are made from force sensingresistance film.
 10. The system of claim 6 wherein said position andweight sensors are positioned in a checkerboard pattern.
 11. The systemof claim 6 wherein said airbag assembly includes a source of gas which,when actuated, provides gas to inflate said airbag and wherein saidsystem further includes a vent valve connected to said source of gas andelectrically connected to said control means, said control meanscontrolling said vent valve so as to vent gas from said gas source inresponse to sensed weight of the occupant.
 12. The system of claim 6wherein said airbag assembly includes two separate gas sources which,when individually actuated, provide gas to inflate said airbag, saidcontrol means including means to control whether one or both gas sourcesare actuated in response to sensed weight of the occupant.
 13. Thesystem of claim 12 further including two vent valves, each gas sourcehaving an associated vent valve, said control means being connected toeach vent valve for controlling venting of gas from the two gas sourcesin response to the sensed weight of the occupant.
 14. The system ofclaim 6 wherein said control means includes means to disable deploymentof said airbag if it is determined that an occupant is sitting at anineffective protection location.
 15. The apparatus of claim 1 furtherincluding means for driving certain of said films of said sensingelements into oscillation, contact by an associated contacting meansattenuating oscillations of said certain of said films, said controlmeans including means for monitoring oscillations of said certain ofsaid films driven into oscillation.
 16. The occupant sensing apparatusof claim 1 wherein certain of said films are made from a piezoelectricfilm, and said controller means includes means for providing an electriccurrent to said piezoelectric films in a manner so as to make saidcertain of said films oscillate, with contact between said contactingmeans and said certain of said films attenuating said oscillations, andsaid controller means further including means for providing a firstsignal indicative of no occupant being present, a second signalindicative of an occupant being present, and a third signal indicativeof a disconnection between said controller means and said certain ofsaid films, said signals being provided in response to detectedoscillations of said certain of said films.